4.5 The DC generator in Problem 4.3 rotates at 1500 rpm, and it delivers rated current at rated terminal voltage. The field winding is connected to a 120 V supply.
(a) Determine the value of the field current.
(b) Determine the value of Rfc required.
4.3 is for reference only.
4.3 A DC machine (6 kW, 120 V, 1200 rpm) has the following magnetization characteristics at 1200 rpm.
If
(A)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.8
1.0 1.2
Ea
(V)
5
20
40
60
79
93
102
114 120
125
The machine parameters are Ra = 0.2 Ω, Rfw = 100 Ω. The machine is driven at 1200 rpm and is separately excited. The field current is adjusted at If = 0.8 A. A load resistance RL = 2 Ω is connected to the armature terminals. Neglect armature reaction effect.
(a) Determine the quantity KaΦ for the machine.
(b) Determine Ea and Ia.
(c) Determine torque T and load power PL.